Add support for interactive PDF decryption

lisp/pdf-info.el

@@ -992,7 +992,20 @@ This command is rarely needed, see also `pdf-info-open'."
             (run-hooks 'pdf-info-close-document-hook))
         (with-temp-buffer
           (run-hooks 'pdf-info-close-document-hook))))))
-
+
+(defun pdf-info-encrypted-p (&optional file-or-buffer)
+  "Return non-nil if FILE-OR-BUFFER requires a password.
+
+Note: This function returns nil, if the document is encrypted,
+but was already opened (presumably using a password)."
+
+  (condition-case err
+      (pdf-info-open
+       (pdf-info--normalize-file-or-buffer file-or-buffer))
+    (error (or (string-match-p
+                ":Document is encrypted\\'" (cadr err))
+               (signal (car err) (cdr err))))))
+
 (defun pdf-info-metadata (&optional file-or-buffer)
   "Extract the metadata from the document FILE-OR-BUFFER.
 

lisp/pdf-view.el

@@ -29,6 +29,7 @@
 (require 'pdf-cache)
 (require 'jka-compr)
 (require 'bookmark)
+(require 'password-cache)
 
 
 ;; * ================================================================== *
@@ -350,9 +351,23 @@ PNG images in Emacs buffers."
             'pdf-view-new-window-function nil t)
   (image-mode-setup-winprops)
 
+  ;; Decryption needs to be done before any other function calls into
+  ;; pdf-info.el .
+  (pdf-view-decrypt-document)
   ;; Setup initial page and start display
   (pdf-view-goto-page (or (pdf-view-current-page) 1)))
 
+(defun pdf-view-decrypt-document ()
+  "Read a password, if the document is encrypted and open it."
+  (interactive)
+  (when (pdf-info-encrypted-p)
+    (let* ((key (concat "/pdf-tools" (buffer-file-name)))
+           (password (password-read (format "Enter password for `%s': "
+                                            (buffer-file-name))
+                                    key)))
+      (pdf-info-open nil password)
+      (password-cache-add key password))))
+
 (defun pdf-view-buffer-file-name ()
   "Return the local filename of the PDF in the current buffer.